Posted on November 4, 2024
As the effects of a changing climate continue to be felt along our nation’s coastlines, civil works and military planners face mounting obstacles. Coastal resiliency and flood risk management are at the forefront like never before, but as conditions change, planners need help assessing these areas to ensure the measures they put into place will still be effective, not just 10 or 20 years down the road, but 50 to 100 years in the future.
Researchers at the U.S. Army Corps of Engineers (USACE) are working on a set of tools to assist coastal planners in forecasting the evolution of coastlines and coastal dunes to help inform decision making and basic planning efforts. Coastal dunes are important as they protect houses, infrastructure and roads from flooding during coastal storms.
“Generally, behind the beach there’s often an area that’s much higher and vegetated,” said Nick Cohn, a research oceanographer with the U.S. Army Engineer Research and Development Center (ERDC). “That vegetated region is referred to as the foredune. We typically consider it to be distinct from the beach, because rather than being driven by what waves do, its form is primarily controlled by vegetation and wind effects.”
Cohn and his ERDC teammate, research civil engineer Dylan Anderson, have created numerical models that focus on the coastal processes that determine whether these structures will be present or absent or whether they’re going to grow or erode over time.
“A lot of what we work on is thinking about how different processes — the interaction of storms, sea level rise, eroding shorelines and complex ecological interactions — actually drive the creation of that landform,” Cohn said. “Our goal is to ultimately predict decades or even centuries from now what the landscape is going to look like based on our best understanding of science and engineering.”
Creating a synthetic version to predict how dunes will evolve in the future is an all-encompassing approach.
“It’s not just the timing of a storm, but also the conditions that happen in between two storms,” Anderson said. “We created an efficient model based on synthetic time series of weather patterns such that you can simulate a variety of potential versions of the future. That weather can then be statistically downscaled to provide future waves and winds that the dune dynamically responds to.”
With thousands of different future scenarios at their fingertips, planners can see a version of their coastline where dunes are exposed to hurricanes in back-to-back years versus a period with a 10-year gap between hurricanes. These hypothetical scenarios are useful for risk-based planning efforts USACE is moving towards.
“You can see your best-case scenario, your worst-case scenario and your most likely scenario,” said Anderson. “By identifying that spread we quantify likelihoods and can let a planner design around the project’s acceptable risk level.”
Having completed projects at ERDC’s Field Research Facility in Duck, North Carolina, and Tyndall Air Force Base in Florida, the team is constantly working on adding additional features to be more applicable to other physical settings, including expanding to other military bases and civil works projects around the country.
“The reality is site conditions are different across the nation,” Cohn said. “All these modeling tools enable the development of site-specific solutions by synthesizing all of the relevant environmental and physical processes that drive the short and long-term evolution to dunes, and therefore, produce outputs that can inform sound, practical solutions in one location that may not necessarily work in another, whether it’s for civil works planners or military installations.”
For planners this comes as good news as coastal managers are constantly looking for low-cost, nature-based solutions that can limit flood exposure during storms.
“It’s a new paradigm that coastal geomorphology and hazards tools are capable of simulating landform evolution not just at the time scale of storms, but across the lifespans useful for USACE-planning decisions related to flood risk management and ecosystem services,” said Cohn. “These capabilities push the boundaries to enable asking and answering questions about climate change and sea level rise and future storm effects on the efficacy of natural infrastructure along the nation’s coasts. All these morphodynamic processes are really complicated, but at the end of the day this research is working towards reliable and scalable capabilities that allow people to think about a wide range of potential future outcomes in the absence of interventions and when including coastal management alternatives.”
“The future is really uncertain, and rather than planning for one future or even 10 futures, we need efficient tools that can see all of the possible futures, so that we’re more prepared,” added Anderson.
“With the current emphasis on engineering with nature and using nature-based solutions and concepts for coastal management, planners need good quantitative tools,” said Cohn. “These numerical models fill that niche in terms of being able to do that in a pretty fast and approachable way. Having these predictive tools where we can go to any location and get some sense of what’s going to happen is very exciting.”
